What factor largely determines the abuse potential of a drug?

The factor that largely determines the abuse potential of a drug is the speed of action and duration of effects. When a drug produces effects quickly and intensely, it is more likely to be abused. This rapid onset can reinforce the behavior of using the drug, as users may chase the initial euphoria or desired effects, leading to increased frequency and quantity of use.

Additionally, a drug's duration of effects impacts how often it is used. If a drug wears off quickly, individuals may feel compelled to use it again soon after, further contributing to a cycle of misuse. This relationship between the pharmacokinetics of the drug—how quickly it acts and how long it lasts—and its likelihood of being abused underscores why this factor is crucial in assessing potential abuse.

In contrast, while factors like age of first use, cost, and legality can influence drug use behaviors and patterns, they do not directly measure the inherent properties of the drug that contribute to its potential for abuse in the same way that speed and duration do.